Worldwide, the vast majority of new infections with HIV are acquired through sexual transmission, the major route of transmission to the 16.4 million infected women. Compounds that are developed for topical use to prevent HIV transmission to (microbicides) offer a promising alternative while awaiting the development of an effective vaccine. One such compound, sodium dimandelic acid ether (SAMMA), efficiently inhibits laboratory-adapted as well as primary isolates of HIV in primary cells including CD4+ T-cells as well as PBMC-derived macrophages. It has potent activity against herpes simplex virus, the sexually transmitted disease that is a major co- factor for HIV. Furthermore, it inhibits sperm function and prevents fertilization in the rabbit with no apparent cytotoxicity. The goal of Project I is to define the full scope and mechanism of HIV-1 inhibition of the candidate topical microbicide, SAMMA, as well as rationally designed derivatives and ultimately purified isomers. A major focus will be in utilizing single-cycle infection to carefully determine site of action in the viral life-cycle and primary cells relevant to initial infection (T-cells, macrophages and dendritic cells) as well as primary viral isolates to assess antiviral potential in cell-free and cell-associated infection. Because preliminary work is consistent with SAMMA working on early attachment and entry steps. the ability of the compound to inhibit non-specific and specific interactions between the virus and the cell that occur during this process will be studied. Interactions between the compound and the virus and envelope protein as well as the compound and cells surface components involved in entry will be studied. Lastly, it is anticipated that topical microbicides will be used repeatedly by infected as well as uninfected individuals resulting in chronic exposure of replicating virus to drugs. The potential, therefore, exists under, selective pressure to generate variants relatively resistant to drug. SAMMA-resistant isolates will be derived and characterized to gain a better understanding of the mechanism(s) of inhibition as wells as the potential for generating resistance and cross-resistance to related compounds in vivo. The proposed studies will define the full my inhibitory potential of SAMMA as well as define critical structural/functional relationships in this unique class of compounds.